The present invention relates generally to a packing container opening arrangement. More specifically, the present invention relates to an opening arrangement on packing containers of the type which has a sealing fin extending over the top end wall of the packing container, and in which a plastic-covered packing material is joined inside-to-inside in a sealing bond.
A common form of packing container for the distribution of milk, fruit juice and other liquid food products is manufactured from a web of paper, coated on both sides with plastic material, this web being formed into a tube by joining together the longitudinal edges of the web in an overlap joint. Thereafter the tube is filled with the intended contents and is transversely sealed by means of repeated flattening and transverse sealing operations along zones situated at a distance from one another and forming a right angle to the longitudinal direction of the tube. The sealed portions of the tube can then be separated by means of cuts in the sealing zones, whereupon the packing units formed may be given parallelepipedic shape, mostly by compression forming and folding of the packing material along crease lines arranged beforehand. In the folding and forming process double-walled, triangular lugs are produced at four of the packages corners, which can be folded in against, and sealed to, the side and end walls respectively of the packing container.
A packing container of the type mentioned here will be provided with a longitudinal overlap joint, that is to say the joint which constitutes the longitudinal joint of the tube, and transverse finlike sealing joints by which the packing material is joined inside-to-inside. The transverse and longitudinal sealing joints will cross one another on the top and bottom end surfaces of the packing container.
In packing containers of the type mentioned here, mostly one of the triangular lugs is used as an emptying opening, and in general the opening is created by folding the triangular lug up from its position resting against the packing container. The triangular fin is then torn up or cut in some manner so that a channel connecting to the interior of the package is obtained.
Since this tearing up of the said triangular lug along a prepared perforation may involve certain inconveniences, and as a cutting off of the fin presupposes the presence of a tool, it has been suggested instead to solve the problem in such a manner that a tear-wire or a tear-strip is inserted into the sealing fin from the tip of the triangular lug serving as an emptying opening and up to, and past, the crossing point between the longitudinal joint and the transverse joint, so that the tear-wire or tear-strip is accessible from the outside of the package. With the help of such a tear-wire or tear-strip it is thus possible to cut up the sealing joint in the sealing fin, so that an emptying opening is produced. Such a tear-up arrangement is known, for example, from Swedish Pat. No. 402,899.
This form of package opening with the help of a wire or tear-strip, where the wire or tear-strip is to rip through the seal produced in order to form an emptying opening, has not proved to function fully satisfactorily. Primarily, this is because the tear-tape or tear-strip often fails to cut straight through the sealing joint, but instead cuts between the paper material and the plastic covering of either of the material layers. This means that the raw fiber surface of the paper material is exposed, so that, on pouring out the contents, the latter come into contact with the raw paper surface which then rapidly becomes soaked and loses its rigidity. Among other inconveniences, it may be mentioned that relatively great forces are required for the ripping up of the sealing joint. Also, it happens not infrequently that the tear-wire, instead of tearing within the actual joint, rips apart the paper layer on one side of the sealing fin, that is to say it "runs off the rails".
The disadvantages mentioned above can be avoided with an arrangement in accordance with the present invention, in which, at least along a part of the sealing fin, the packing material layers facing towards each other include between them a strip, inserted in the sealing fin. The strip includes a central layer of a non-extensible, or only slightly extensible, material which is provided on both sides with covering layers of the same, or similar plastic material as that present on the inside of the packing material. The covering layers on the strip are sealed by heat-sealing to the inner plastic layer of the packing material with good adhesive strength, while the adhesive force between the central layer of the strip and the covering layers on the strip is inferior to the adhesive force between the covering layer of the strip and the inner layer of the package material.